Half-duplex telegraph repeater



April 1, 1958 GT. ROYDEN 2,829,200

HALF-DUPLEX TELEGRAPH REPEATER Filed 001;. 3, 1955 R5 2/195 5 W- k a TELfPRl/Wf R/ TPR +laov, fl 5 IEOV.

' INVENTOR 6 65 r owe/v United States Patent Patented Apr. 1, 1958 HALF-DUPLEX TELEGRAPH REPEATER Application October 3, 1955, Serial No. 537,948

4 Claims. (Cl. 17 8--70) My invention relates to half-duplex telegraph repeaters.

When using half-duplex telegraph repeaters for connecting a subscribers teleprinter to radio transmitting and receiving terminal facilities, tests have shown that under certain conditions the operating margin was reduceed to such an extent as to make the service unreliable. This impairment was found to be most pronounced when working with teleprinters having pulling selector magnets and with long interconnecting extensions through exchange cables. Such an impairment is particularly undesirable where a radio circuit is involved due to the multi-path distortion which is sometimes prevalent.

Oscillograph observations of the keyed telegraph current indicated superfluous or extraneous surges after the receiving relay of the repeater moved from its marking to its spacing position. In other words, the line current did not drop to zero immediately after the receiving relay switched the line from battery to ground. It has been found that this elongation, resulting in the extraneous surges, is due to the electrical charge in the capacity of the subscribers line loop circuit flowing to ground via the tongue and grounded space contact of the receiving relay.

Further tests indicated that the impairment in question could be avoided by opening the line circuit on space signals instead of grounding it. One method which was tried involved the use of a transmitting relay having more than two windings. Another alternate method required the employment of a modified receiving relay having more than one contact set.

A primary object of my invention is to provide a halfduplex telegraph repeater in which the line is opened on received space signals, but employing standard-type polar telegraph relays each having but two windings and only one set of contacts. I

According to a feature of my invention the armature tongue of the receiving relay is connected to the ungrounded side of the current supply source and one end of the operating winding of the transmitting relay is connected to the marking contact of the receiving relay so that the line circuit is opened when the receiving relay goes to space. At the same time the current through the biassing Winding of the transmitting relay is reversed in direction over the spacing contact of the receiving relay so as to hold the transmitting relay in its marking position during keying of the receiving relay.

The above and other objects and features of my invention will be better understood from the following description taken in conjunction with the accompanying drawing which is a circuit diagram of one embodiment of my invention.

Referring now to the drawing, the repeater illustrated comprises a receiving relay K1 and a transmitting relay K2, both of which are standard polar telegraph relays of well-known kind each having an upper operating winding and a lower biassing winding, and only one set of contacts comprising an armature tongue and front and back stationary contacts.

The upper operating winding of the receiving relay K1 is connected to the receiving terminals 1, 2 and its lower biassing winding is connected across a suitable source of direct current, for example, volts, inseries with a resistor R1 which determines the magnitude of the biassing current.

One end of the upper operating winding of the transmitting relay K2 is connected via a variable resistor R5 to the line 3 leading to the subscribers teleprinter TPR.

The other end is connected to the mark contact 4 of the receiving relay Kl. One end of the biassing winding of relay K2 is connected to the space contact 5 of relay K1 and one end of a variable resistor R2, and the other end of this winding is connected to the junction of two resistors R3 and R4 which are connected acrossthe direct current supply.

Line current is taken from +120 v. to the tongue 6 of the receiving relay K1 and thence over the operating Winding of the transmitting relay K2, a resistor R5 and the line .3 to the subscribers teleprinter TPR, returning via ground to 120 v. Resistor R5 is preferably adjusted so that the current in the line is 60 milliamperes.

(Jurrent also flows from +120 v., through the voltage divider formed by resistors R3 and R4 to -120 v. When the tongue 6 of relay K1 is on its marking contact, current also flows from the junction of resistors R3 and R4 through the lower biassing winding of the transmitting relay K2 returning to 120 v. via resistor R2. Relay K2, therefore, remains in its marking condition.

During receiving over the terminals 1-2, when the current in the operating Winding of receiving relay K1 is interrupted, the tongue 6 moves from its marking contact 4 to its spacing contact 5 under the influence of its biassing winding. The line current is thus interrupted and signals are sent to the teleprinter TPR. It will be noted that as soon as the tongue 6 of relay K1 leaves the marking contact 4, the lower end of the operating winding of relay K2 is completely disconnected. The energy of the line can result only in a stored in the capacity flow of current through the teleprinter, and thus the extraneous elongation of the signal due to the long time constant of the resistor P5 times the capacitance of the line, is not present.

As soon as the tongue 6 of relay K1 engages the spacing contact 5, current flows from +120 v. through contact 5, the lower biassing winding of transmitting relay K2 and resistor R4 to 120 v., and at the same time the current in the upper operating winding of relay K2 drops from 60 milliamperes to zero. The current in the biassing winding is thus reversed in direction and since the magnet field is now in the same direction as that set up when the upper winding is energized, the transmitting relay K2 will remain in its marking condition while relay K1 is keying.

The resistor R2, which is in shunt to the biassing winding of relay K2 in the spacing position of relay K1, may be adjusted to control the magnitude of the biassing current, or alternatively, the resistor R4 may be adjustable for that purpose. The resistors R2 and R3 (or R4) should be adjusted in turn and then readjusted so that the average of the biassing currents flowing through the lower winding of relay K2 when the relay K1 is on mark and on space, respectively, is one half of the line current when relay K1 is on mark.

When transmitting from the subscribers teleprinter TPR, the current over the line 3 and the upper operating winding of the transmitting relay K2 is interrupted. The current in the lower biassing winding of relay K2 then causes the tongue 7 of that relay to move from its marking contact 8 to its spacing contact 9 whereby signals are transmitted over the send terminals 10, 11,

While I have described above the principles of my invention in connection with specific apparatus, itis to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention.

What is claimed is:

l. A half-duplex telegraph repeater comprising a receiving relay and a transmitting relay each having an op erating winding and a biassing winding and an armature tongue cooperating with marking and spacing contacts, a source of current having one side grounded, receiving terminals, sending terminals, a line terminal, means for connecting said receiving terminals to the operating winding of said receiving relay, means for energizing the biassing winding of said receiving relay from said source of current, a connection from the ungrouncied side of said source of current to the armature tongue of said receiving relay, a connection from the marking contact of said receiving relay to one end of the operating winding of said transmitting relay, a connection from the other end of said last-mentioned winding to said line terminal, means including a variable potentiometer connected across said source and to said transmitting relay for reversing the direction of the current in the biassing winding of said transmitting relay when the armature tongue of said receiving relay moves from its marking contact to its spacing Contact, and connections from said sending terminals to the armature tongue and marking contact respectively of said transmitting relay.

2. A half-duplex telegraph repeater comprising a receiving relay and a transmitting relay each having an operating winding and a biassing Winding and an armature tongue cooperating with marking and spacing contacts, a source of current having one side grounded, receiving terminals, sending terminals, a line terminal, means for connecting said receiving terminals to the operating winding of said receiving relay, means for energizing the biassing winding of said receiving relay from said source of current, a connection from the ungrounded side of said source of current to the armature tongue of said receiving relay, a connection from the marking contact of said receiving relay to one end of the operating winding of said transmitting relay, a connection from the other end of said last-mentioned winding to said line terminal, a circuit including the armature tongue and 4 spacing contact of said receiving relay and the biassing winding of said transmitting relay, whereby said transmitting relay is held in its marking position during the keying of said receiving relay, and connections from said ending terminals to the armature tongue and marking contact, respectively, of said transmitting relay.

3. A half-duplex telegraph repeater comprising a receiving relay and a transmitting relay each having an operating winding and a biassing winding and an armature tongue cooperating with marking and spacing contacts, a source of current having one side grounded, receiving terminals, sending terminals, a line terminal, means for connecting said receiving terminals to the operating winding of said receiving relay, means for energizing the biassing winding of said receiving relay from said source of current, a connection from the ungrounded side of said source of current to the armature tongue of said receiving relay, a connection from the marking contact of said receiving relay to one end of the operating winding of said transmitting relay, :1 connection from the other end of said last-mentioned winding to said line terminal, first and second resistors connected across said source of current, a connection from one end of the biassing winding of said transmitting relay to the junction point of said first and second resistors, a third resistor, a connection from the other end of said last-mentioned biassing winding to the spacing contact of said receiving relay, a connection including said third resistor from the grounded side of said source of current to the spacing contact of said receiving relay, and connections from said sending terminals to the armature tongue and marking contact, respectively, of said transmitting relay.

4. A half-duplex telegraph repeater according to claim 3, wherein one of said first and second resistors and said third resistor are adjusted to he of such magnitude that the average value of the blessing currents flowing through the biassing winding of the said transmitting relay when the said receiving relay is in its marking and spacing positions, respectively, is one half of the line current when the said receiving relay is in its marking position.

References Cited in the file of this patent UNITED STATES PATENTS 2,609,453 Rea Sept. 2, 1952 

